A power
plant or a power generating station, is basically an
industrial location that is utilized for the generation and distribution of electric power in mass scale,
usually in the order of several 1000 Watts. These are generally located at the
sub-urban regions or several kilometers away
from the cities or the load centers, because of
its requisites like huge land and water demand, along with several operating
constraints like the waste disposal etc.
For this reason, a power generating station has to not only take care of
efficient generation but also the fact that the power is transmitted
efficiently over the entire distance. And that’s why, the transformer switch yard to
regulate transmission voltage also becomes an
integral part of the power plant.
At
the center of it, however, nearly all power
generating stations has an AC generator or an alternator, which is basically a rotating machine that is equipped to
convert energy from the mechanical domain (rotating turbine) into electrical
domain by creating relative motion between a magnetic field and the conductors. The energy
source harnessed to turn the generator shaft varies widely, and is chiefly
dependent on the type of fuel used.
A power plant can be of several types depending mainly on the type of fuel
used. Since for the purpose of bulk power generation, only thermal, nuclear and
hydro power comes handy, therefore a power generating station can be broadly
classified in the 3 above mentioned types. Let us have a look in these types
of power stations in details.
A thermal power station or a coal fired thermal
power plant is
by far, the most conventional method of generating electric power with reasonably
high efficiency. It uses coal as the primary fuel to boil the water available
tosuperheated steam for driving the steam turbine. The
steam turbine is then mechanically coupled to an alternator rotor, the rotation
of which results in the generation of electric power. Generally in India,
bituminous coal or brown coal are used as fuel of boiler which has volatile
content ranging from 8 to 33 % and ash content 5 to 16 %. To enhance the
thermal efficiency of the plant, the coal is used in the boiler in its
pulverized form.
In coal fired thermal power plant, steam is obtained in very high pressure
inside the steam
boiler by
burning the pulverized coal. This steam is then super heated in the super heater to extreme high
temperature. This super heatedsteam is then
allowed to enter into the turbine, as the turbine blades are rotated by the
pressure of the steam. The turbine is mechanically coupled with alternator in a
way that its rotor will rotate with the rotation of turbine blades. After
entering into the turbine, the steam pressure suddenly falls leading to corresponding
increase in the steam volume. After having imparted energy into the turbine
rotors, the steam is made to pass out of the turbine blades into the steam condenser of turbine. In the condenser,
cold water at ambient temperature is circulated with the help of pump which
leads to the condensation of the low pressure wet steam. Then this condensed
water is further supplied to low pressure water heater where the low pressure
steam increases the temperature of this feed water, it is again heated in high
pressure. This outlines the basic working methodology of a thermal power plant.
The nuclear power generating stations are similar to the thermal stations in
more ways than one. How ever, the exception here
is that, radioactive elements like Uranium and thorium are used as the primary
fuel in place of coal. Also in a Nuclear station
the furnace and the boiler are replaced by the nuclear reactor and the heat
exchanger tubes.
For the
process of nuclear power generation, the radioactive fuels are made to undergo
fission reaction within the nuclear reactors. The fission reaction, propagates
like a controlled chain reaction and is accompanied by unprecedented amount of
energy produced, which is manifested in the form of heat. This heat is then
transferred to the water present in the heat exchanger tubes. As a
result, super heated steam at very high
temperature is produced.
Once the
process of steam formation is accomplished, the remaining process is exactly
similar to a thermal power plant, as this steam will further drive the turbine
blades to generate electricity.
In Hydro-electric plants the energy of the falling water is utilized to drive
the turbine which in turn runs the generator to produce electricity. Rain
falling upon the earth’s surface has potential energy relative to the oceans
towards which it flows. This energy is converted to shaft work where the water
falls through an appreciable vertical distance. The hydraulic power is
therefore a naturally available renewable energy given by the eqn:
P = gρ QH
Where, g = acceleration due to gravity = 9.81 m/sec 2
ρ = density of water = 1000 kg/m 3
H = height of fall of water.
This power is utilized for rotating the alternator shaft, to convert it to
equivalent electrical energy.
An important point to be noted is that, the hydro-electric plants are of much
lower capacity compared to their thermal or nuclear counterpart. For this
reason hydro plants are generally used in scheduling with thermal stations, to
serve the load during peak hours. They in a way assist the thermal or the
nuclear plant to deliver power efficiently during periods of peak hours.
As mentioned above, depending on the type of fuel used, the power generating
stations as well as the types of power generation are classified. Therefore the
3 major classifications for power production in reasonably large scale are :-
1. Thermal power generation.
2. Nuclear power
generation.
3. Hydro-electric power
generation.
Apart from these major types of power generations, we can resort to small scale
generation techniques as well, to serve the discrete demands. These are often
referred to as the alternative methods of power generation and can be
classified as :-
1. Solar power
generation. (making use of the available solar energy)
2. Geo-thermal power
generation. (Energy available in the Earth’s crust)
3. Tidal power generation.
These alternative sources of generation has been given due importance in the
last few decades owing to the depleting amount of the natural fuels available
to us. In the centuries to come, a stage might be reached when several
countries across the globe would run out of their entire reserve for fossil
fuels. The only way forward would then lie in the mercy of these alternative
sources of energy which might play an instrumental role in shaping the energy
supplies of the future. For this reason these might rightfully be referred as
the energy of the future.